Stair pressurization with open doors

Stair pressurization with open doors

Stair pressurization with open doors

I'm trying to design pressurization system for stairwell.actually, We follow IBC AND ASHRAE IN WHICH I can not find and specific number of doors to be open while designing the system to calculate the pressurization fan capacity.My question is regarding the open door airflow.I have seen many engineers design the system so that the airflow velocity through the open door is around .75 m/s to hold smoke back from entering the stairwell which would increase the fan capacity to meet this demand.But i can not find such a criteria in Ashrae at all.A solved example of pressurization system using Contam software shows that, it is only enough to have a positive pressure difference across open door to guarantee that smoke is held back from entering the stairwell.Am i getting it right? because i'm confused.

RE: Stair pressurization with open doors

I used 2 doors open. Foolish to think about saving money when lives could be at stake. Use constant speed fan but with bypass damper to exhaust or recirculate air, controlled by stairwell pressure sensor.

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